Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$126.87	3.516%	$131.3307	$131.33	$131.35	$131.30
Purchase #2	$219.41	13.126%	$248.2098	$248.21	$248.20	$248.20
Purchase #3	$159.51	9.773%	$175.0989	$175.10	$175.10	$175.10
Purchase #4	$219.75	11.702%	$245.4651	$245.47	$245.45	$245.50
Purchase #5	$163.56	10.642%	$180.9661	$180.97	$180.95	$181.00
Purchase #6	$55.70	6.809%	$59.4926	$59.49	$59.50	$59.50
Purchase #7	$111.28	5.672%	$117.5918	$117.59	$117.60	$117.60
7 purchase totals =	$1,056.08		$1,158.1550	$1,158.16	$1,158.15	$1,158.20